Exposing the darker side of people is something I find fascinating," says Emeli Sandé, and she's not the only one. The singer-songwriter, who entered the charts at No 2 last week with her debut single Heaven, is one of a number of female artists turning commercial pop sombre with songs of pain and despair.

The biggest-selling single of 2010 was the none-more-sorrowful Love the Way You Lie by Eminem featuring Rihanna, co-written by Skylar Grey, a 25-year-old LA goth girl who hangs out with Marilyn Manson. And rising British star Kyla La Grange sings about "feeling sad and getting fucked up" and is obsessed with death. Even Florence Welch's new single, What the Water Gave Me, alludes to the suicide by drowning of Virginia Woolf, a favourite author of both Sandé and La Grange, and takes its title from a painting by Frida Kahlo, the tormented surrealist Mexican painter whose face happens to be tattooed on Sandé's right forearm (A Room of One's Own, a Woolf title, appears on the other).

It's extraordinary, then, that Sandé's background is in songwriting for the likes of Tinie Tempah, Tinchy Stryder, Chipmunk, Cheryl Cole, Cher Lloyd, Leona Lewis, the Saturdays and Susan Boyle. Do her regular commissions from Syco (she's Simon Cowell's favourite new songwriter), mean she feels the need to turn to a different side of a character for her own recordings?

"A song is always going to have my slant on it," she says, in a cafe near her flat in east London, "but it's not intentional, no. I just write from an honest place that hopefully everyone can relate to. I don't think he [Cowell] wants darkness, he wants honesty."

Does she think about the person that she's writing for and try to get under their skin?

"I would never think: 'Oh, I'm Susan Boyle, what would I want to say?' It's more like, if I was sitting here having a chat with Susan, what would we talk about? The same goes for the Saturdays – I didn't just write a song for teenage girls."

There seems to have been a greater sense of identification with Cher Lloyd. "Yeah, the one I wrote for her, A Lifetime, really reflects her," she says. "She's not just some pop thing. There's a real darkness to her, a rawness. I really connected to her."

Is Sandé Britain's go-to girl for bespoke darkness? She laughs.

"I'm going to write a happy song one day," she promises. "You can be happy but still be smart about it."

Meanwhile, she's writing songs such as Kill the Boy, which includes graphic imagery ("Skin will turn as cold as ice/ When his lungs collapse enough there will be no more breathing") that would seem chilling on a leftfield release, let alone one destined for the shelves at Tesco.

Sandé was a medical student at Glasgow University, specialising in clinical neuroscience (she got three-quarters of the way through her degree), which perhaps explains her predilection for the pathology of desire. "I've always been into dark writers – Sylvia Plath's stuff, Virginia Woolf – and Frida Kahlo's art," she says. "It shows that really graphic side of people. Studying neurology you learn about how we are instinctively. I found it fascinating how people can have these mental breakdowns. How can this whole different side of your character come from nowhere? Why would you cheat on this person and feel like killing them?"

Despite all this dark stuff, Sandé sees no disconnect between the sorts of things she wants to say and reaching a wide audience, which is why she ensures her songs are easy on the ear. "I hate hearing discordant music that is too arty," she says. "I want people to sing along."

Kyla La Grange – whose father, like Sandé's, is from South Africa, and who has a philosophy degree from Cambridge – also wants to achieve pop success, without soft-soaping her subject matter.

"I love people like Cat Power," says La Grange, "but I have far more of a commercial sensibility."

La Grange also shares Sandé's interest in, if not the dark arts (although she does admit to "loving the idea of witchcraft and paganism"), then dark art, which comes out in her music.

"For as long as I remember I've written songs about miserable things," she says. "I have so many booklets of songs from when I was 12 or 13, and they're so fucking depressing! I wasn't a very happy child, which led me to write songs."

La Grange's songs can veer wildly between intimate folk and a more epic style informed by Bonnie Tyler's Total Eclipse of the Heart. "Some of my songs are sad and introverted," she says, "but others need big driving drums and shouting, because sometimes when I write my nerves are shredded and I feel as though my head's going to explode."

What is likely to shred her nerves?

"Lots of things," she says. "I'm a worrier. I can't switch it off. Death – that's the big one! Oh my God. Every night when I'm trying to sleep I get this vision of eternal blackness in my head, about how one day everyone alive will be gone. Then I might drop off, only to wake up shaking."

That first happened when she was eight, she says. "My parents laugh when they tell this story, about how I came downstairs one night, crying that we were all going to die," she recalls. "Now I try and block them off as soon as I feel the first tendrils of these thoughts entering my brain."

La Grange isn't sure why there might be a vogue for excoriating self-expression right now – "Maybe it's the credit crunch," she offers – while Sandé fears it might become a gimmick.

"Sometimes people want to be dark to be fashionable," says Sandé, who is, nevertheless, delighted that women are being afforded the opportunity to spill their souls on the biggest stages. "It's a liberating time. It's a lot more acceptable for a woman to say: 'You know what? I feel shit today. I feel mental.'"

The third in this troika is Skylar Grey who – with tracks such as Weirdo, Building a Monster and Beautiful Nightmare – is popularising angst-ridden soul-searching as though Alanis Morissette never went out of fashion. She's also added some emo heft to hip-hop, penning not just Love the Way You Lie but also Coming Home for P Diddy's Diddy-Dirty Money, and guesting on Dr Dre's I Need a Doctor, at the behest of Eminem, who insisted it be Grey and not the mooted Lady Gaga.

After beginning her career as a winsome but unsuccessful teenage troubadour, under her real name of Holly Brook, things changed when Grey went monochrome.

"Everything was going wrong in my life," she recalls over sandwiches in a London hotel. "So I threw out every piece of clothing in my closet that had colour in it. Any shade of grey from white to black I kept." The change is given expression in the video for Dance Without You, which shows one girl (Brook) convulsing as another (Grey) bursts out of her body.

"It's Skylar inside of Holly trying to get out," she explains the metaphor for her recent rebirth and name change. Is there any of Holly Brook left inside of her? She pauses. "Yeah," she says, "I have Holly moments. But Skylar Grey always wins."

In fact, she and Manson are friends. He even suggested the title of her debut album, Invinsible, with that extra "n" because it's about self-empowerment. It's strange to think that such a hot commercial property spends her days hanging out at Manson's house perusing his collection of books on torture and watching extreme-sex movies (she once had a job editing porn videos). "I find them interesting," she says. "It's a learning experience."

Even stranger are the slew of odd and disturbing experiences she endured in the runup to her recent success. In 2008 alone, she was run over by a car, attacked by a bear while camping, had her cat stolen by satanists and lived in a house infested with black widow spiders. Her flatmate at the time was psychotic and "wouldn't let me leave – he even drained my car of gas", so she tried to kill him by going onto the roof and dropping a coffee jug on his head. Luckily, it missed, and she escaped.

Within a year, she met her manager, who gave her the $10,000 she needed to build her own recording studio. A further 12 months down the line and her phone's ringing off the hook. Now all she's got to do is stay alive.

"I'm drawn to dark areas," she says. "It's almost an addiction. I've had suicidal thoughts but I like to experience life, even if it means pain. Pain makes you feel alive. That's why I embrace it."

That raises the question: do tormented people get drawn to the arts, or does art provide the torment? Emeli Sandé isn't sure but says writing "is like a safety valve" without which she would "probably be going slowly mad in a bedroom in Scotland". And she can't help but wonder why many of her favourite artists led such harrowing lives. "A lot of them suffered depression that spiralled out of control, then they died," she says sadly. "It's interesting that there's a high prevalence of bipolar conditions in the arts."

But maybe that's just an exaggerated reflection of the human condition. "We're all flawed," she says, "or addicted to something." Can you be addicted to pain? "You can be addicted to drama, maybe."

The key is to keep the right balance between honest artistry and accessibility. And not to suffer too much for your art.

"I don't want to lose everybody on the journey," Sandé says. "I don't want to get too introspective, or what's the point? Writing something to sing in your bedroom? That's just healing yourself."

What does she think about the death of Amy Winehouse?

"She was a legend, and I admired her as a writer," she considers. "There was a pain to what she was speaking about and I believed her. She could have made average art. But maybe she went too deep and lost control."

Does Sandé control her muse?

"I hope so," she replies. "I hope so."

Emeli Sandé's Heaven is out now – her debut album will be released by EMI in early 2012. Kyla La Grange's Heavy Stone/Lambs is released by Chess Club on 17 October. Skylar Grey's debut single, Invisible, is released by Polydor on 15 September.

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